1. Technical Field
The present invention relates to the art of grinding tree stumps and other materials. More particularly, the invention relates to the art of wheels that are used to grind tree stumps and other materials. Still more particularly, the invention relates to wheels for grinding tree stumps and other materials that provide improved installation, positioning and orientation of cutting tools which are mounted on the wheel, thereby improving the performance and the life of the wheels.
2. Background Art
In order to remove tree stumps and other similar materials from the ground during construction or other work, a stump grinder is typically used. The stump grinder usually includes a driven wheel, which is known as a stump grinding wheel, and specialized cutting tools are mounted on the sides and on the outer periphery of the wheel. When it is desired to remove a stump, the stump grinder is activated, thereby turning or rotating the wheel, and the cutting tools that are mounted on the wheel are brought into contact with the stump. As the wheel rotates, the cutting tools gradually cut and disintegrate the stump, thus removing the stump from the ground.
In the prior art, some particularly effective stump grinders have included cutting tools that have become known in the art as side cutter assemblies. A side cutter assembly typically includes pairs of cutting teeth, in which the teeth of each pair extend through the wheel in opposing directions. More particularly, one tooth of a pair of teeth extends through the wheel so its respective cutting tip protrudes through one side of the wheel, and the other tooth of the pair extends through the wheel so its respective cutting tooth protrudes through the other side of the wheel. Each pair of teeth seats in a pair of mechanical pockets, each one of which is disposed on an opposing side of the wheel. A nut is threaded onto each tooth to securely clamp the teeth to the pockets, and in turn to clamp the pockets to the wheel. In the prior art, about twenty or more side cutter assemblies are mounted on the wheel in helical patterns to maximize cutting efficiency, and each side cutter assembly is mounted on the wheel in a generally circumferentially-extending orientation.
To increase the cutting ability of the stump grinding wheel, some side cutter assemblies have been modified to form peripheral cutter assemblies, which enable cutting teeth to be placed about and to extend from the peripheral edge of the wheel. This is typically accomplished by forming radial slots in the periphery of the wheel and securing the teeth in specialized mechanical pockets, which seat in the radial slots and typically are secured to the wheel by welding. These peripheral cutter assemblies are significant, since they typically make the initial contact with the stump, and also accomplish a significant amount of grinding due to the fact that they are mounted on the fastest-moving part of the wheel, that is, on the periphery of the wheel.
During use of the stump grinder, the fast-moving nature of the peripheral edge of the wheel subjects the wheel periphery and the peripheral cutter assemblies to extreme wear from abrasive materials that are trapped between the rotating wheel and the uncut portion of the stump. While the prior art helical mounting patterns of the circumferentially-extending side cutter assemblies create an excellent cutting pattern, they leave large areas of the periphery of the wheel unprotected, and thus vulnerable to such extreme wear. This wear undesirably shortens the life of the wheel. As a result, there is a need in the art for a stump grinding system that uses a pocket with a new shape, which enables improved positioning, placement and orientation of the side cutter assemblies to protect the peripheral areas of the wheel and thus extend the life of the wheel.
A second disadvantage of prior art stump grinding wheels is the congested location of certain side cutter assembly pockets with respect to other side cutter assembly pockets and to the peripheral cutter assembly pockets. More particularly, in order to optimize the amount of cutting performed by the wheel, side cutter assemblies are mounted in the above-mentioned helical patterns, which extend outwardly to the periphery of the wheel. Some side cutter assemblies may be mounted in close proximity to one another, and such close proximity of circumferentially-oriented assemblies may cause them to interfere with one another and create congested areas. In addition, certain side cutter assemblies are mounted along the periphery of the wheel between the peripheral cutter assemblies in a circumferentially-oriented manner, and the close proximity of the side cutter assemblies with the peripheral cutter assemblies may cause them to interfere with the welds that secure the peripheral cutter assemblies to the wheel, thereby creating additional congested areas. These congested areas may pack with dirt and pieces of the stump, which may in turn cause the wheel to undesirably become unbalanced. An unbalanced wheel often generates severe vibration and thus requires replacement, resulting in increased cost and lost production. As a result, there is a need in the art for a stump grinding wheel having improved positioning, placement and orientation of side cutter assemblies to reduce the potential for creating congested areas along the periphery of the wheel.
A third disadvantage of prior art stump grinding wheels is misalignment of the cutting teeth, which may be created by mounting side cutter assemblies in a circumferentially-oriented manner. More particularly, with prior art stump grinding wheels, the cutting edges of the teeth on one side of a wheel typically are properly aligned to cut a stump, but the teeth on the opposite side of the wheel may not be properly aligned. As described above, a pair of teeth extends through the wheel, with each tooth of the pair extending in opposite directions, and the pair of teeth seats in a pair of mechanical pockets, each one of which is disposed on an opposing side of the wheel. Each tooth includes a cutting edge, which is typically a carbide edge, and optimally is aligned at a desired angle for easy cutting of a stump. This desired cutting angle is measured radially from the center of the wheel.
The circumferential mounting orientation of the side cutter assemblies often impedes uniform alignment of the cutting edges of the teeth, so that the cutting edges on one side of the wheel are undesirably disposed at different angles when compared to the cutting edges on the other side of the wheel. As a result, the cutting edges on one side of the wheel may be uniformly aligned, while the cutting edges on the other side of wheel are not, causing a considerable difference in cutting performance when using the cutting edges on one side of the wheel as compared to using the cutting edges on the other side of the wheel. For example, an operator of a stump grinder using a wheel with such cutting tools may experience smooth cutting when advancing the wheel into the stump one way, which uses the cutting edges on one side of the wheel that are properly aligned. However, when the operator advances the wheel into the stump from the opposite direction, which uses the cutting edges on the other side of the wheel that are not properly aligned, the wheel may bounce, vibrate and/or cut poorly. Such bouncing and vibration can cause damage to the stump grinding machine and lost production. Therefore, there is a need in the art for a stump grinding wheel that provides improved uniform alignment of the edges of the cutting teeth to enable optimum cutting by cutting edges on both sides of the wheel.
A fourth disadvantage of prior art stump grinding wheels is shifting of the alignment of the teeth when they are tightened down. More particularly, each tooth of each side cutter assembly typically includes a square section that seats in a corresponding square recess in its respective mechanical pocket. When the tooth is inserted into the pocket and tightened down with a nut, the square section of the tooth rotates slightly until a wall or corner of the square section meets and seats against a corresponding wall or corner of the recess in the pocket. As described above, the alignment of the cutting edge of each tooth is important. Such slight turning of the tooth in the pocket may cause the cutting edge of the tooth to undesirably turn, resulting in the cutting edges of the teeth on one side of the wheel being at different angles from the cutting edges of the teeth on the other side of the wheel, as measured radially from the center of the wheel. This contributes to the above-described problem of the cutting edges of the teeth cutting well when the operator advances the wheel into the stump one way, but then cutting poorly when the operator advances the wheel into the stump from the opposite direction. As a result, there is a need in the art for a stump grinding wheel that enables the cutting teeth to maintain proper alignment as they are tightened down.
A fifth disadvantage of stump grinding wheels of the prior art is that, while the combination of side cutter assemblies and peripheral cutter assemblies on a wheel works well on large powerful machines, such an aggressive combination of cutter assemblies may cause the wheel to hang up or stall on smaller machines. More particularly, the use of side cutter assemblies and peripheral cutter assemblies, which grab and dig into the stump as they cut, requires a significant amount of power in order to keep the wheel rotating. Since smaller stump grinding machines generate less power than larger machines, the smaller machines may not have enough power to keep the wheel moving as the aggressive combination of side cutter and peripheral cutter assemblies grabs and digs into the stump. In addition, sometimes a wheel having an aggressive combination of side cutter assemblies and peripheral cutter assemblies will move up or climb up on the stump that is being cut, which can upset or overturn a smaller stump grinding machine, potentially damaging the machine. Thus, there is a need in the art for a stump grinding wheel that provides for the optional use of a less aggressive combination of cutting assemblies when a smaller stump grinding machine is employed, while retaining the robustness of the cutting assemblies that are used on larger machines.
As a result, a need exists in the art for a stump grinding wheel that reduces or minimizes the above-described disadvantages. The stump grinding wheel of the present invention satisfies this need.